Apparatus for positioning film or tape wound on reels

ABSTRACT

A switching mechanism including a sliding contact and a pair of movable contacts which control a motor used to drive a film or tape between two reels. A mechanical feedback positions the movable contacts in relationship to linear displacement of the film or tape in accordance with the set position of the sliding contact. An analog computer mechanism comprising a pair of spiral pulleys linearizes the feedback relative to film or tape displacement.

United States'Patent 1191 Priest 14 1 Jan. 9, 1973 541 APPARATUS FORPOSITIONING FILM 3,324,685 6/l967 Schmidt 61 al ..31s/39 0R TAPE WOUNDONREELS 3,069,611 12/1962 was/r16 6131. ..3l8/467 [75] Inventor: LyleGilbert Priest, Palo Alto, Calif. Primary Examiner BenJ-amin D 0b 6 ck[73] Assignee: Information Desigmlnc. A 0rneyCarll-l0ppe etal.

[21] PP 156,660 A switching mechanism including a sliding contact I anda pair of movable contacts which control a motor 52 us. (:1..3l8/467,318/673 used to a fi between two reels- A 51 1111.01. ..G05b1/06 mechaniml feedbad PSitins the movable [58] Field of Search 318/467673 39 in relationship to linear displacement of the film or tape inaccordance with the set position of the sliding contact. An analogcomputer mechanism comprising a [56] References Cited pair of spiralpulleys linearizes the feedback relative to UNITED STATES PATENTS filmor p displacement- 3,614,574 10/1971 Hodges ..3l8/467 7 Claims, 2Drawing Figures PATENTEDJAN 9 ma FIG. .1.

lllllllll ll/ 44 Illllll ll llllllllllll LYLE G. PRIEST lNVENgzl BY FEG.2

ATTORNEYS APPARATUS FOR POSITIONING FILM OR TAPE WOUND ON REELS Thisinvention relates generally to a mechanism for positioning film or tapewound on reels. It has particular application to machines for viewingmicrofilm by selecting a particular picture or frame on a filmstrip andpositioning that particular picture in front of a lens.

In brief, this invention teaches a novel switching mechanism foroperating a motor control circuit including a pair of clutches that maybe selectively engaged to drive a pair of reels and accurately positiona filmstrip for viewing a selected picture or frame. The switchingmechanism comprises a sliding contact and a pair of movable contactswhich are positioned by a mechanical feedback mechanism. The mechanicalfeedback positions the movable contacts in relationship to displacementof the film or tape as it is wound or unwound from a take-up reel. Apair of spiral pulleys,

mechanically linked to the take-up reel serve as an analog computer tolinearize the relationship of mechanical feedback with respect to filmor tape displacement.

One object of the present invention is to provide a novel switchingmechanism for accurately positioning a filmstrip for viewing a selectedpicture or frame.

Anotherobject is to provide a switching mechanism mechanism connects totape reel 23 through an analog computer mechanism 24 to maintain alinear relationship between the rate of tape movement and the rate atwhich belt 13 is moved by pulley 12. A

preferred embodiment of such a device, illustrated in FIG. 2, ishereinafter described.

The control circuit for operating motor 19 and clutches and 21 isdesigned to operate from an AC supply but provides a DC source forenergizing a pair of solenoids and 26 that operate clutches 20 and 21,respectively. The electrical circuit more particularly comprises anoff-0n switch 30, a momentary energizing switch 31 and a holding circuitincluding an SPST relay having a coil 32 which, when energized, closesnormally open contacts 33.

Switching mechanism 10 operates in association with a DPDT relay havinga coil 34 which, when energized,

. operates movable contacts and 36 from points of of the kind describedand more particularly comprising a sliding contact and a pair of movablecontacts and a mechanical feedback for positioning the movable contactsin relationship to linear displacement of the film or tape and inaccordance with the set position of the sliding contact.

A still further object of this invention is to provide apparatus of thekind described including an inexpensive analog computer mechanism forlinearizing the movement of the movable contacts in relationship tolinear displacement of the film or tape.

Other objectsof this invention will become apparent in view of thefollowing detailed description.

In the drawings forming apart of this application and in which likeparts are identified by like reference numerals,

FIG. 1 is a diagrammatic view of a preferred form of apparatus forpracticing this invention including a schematic diagram of a motorcontrol circuit; and

FIG. 2 is a plan view of a mechanical analog computer device used by theinvention for linearizing mechanical feedback.

Referring to FIG. I, a switching mechanism l0'comprises a pair ofpulleys 11 and 12'that are interconnected by a belt 13 formed of twoelectrically conductive portions 13a and 13b, a nonconductive section130 and a nonconductive tensioning spring 13d. Conductive sections 130and 13b serve as movable contacts that engage fixed contacts 16 and 17,respectively. Depending on the rotational positions of pulleys 11 and12, either one of the electrically conductive sections 130 and 13b ornon-conductive section 130 engages a sliding contact 18. The slidingcontact is also movable and is selectively positioned along anelectrically conductive element 18a.

Switching mechanism 10 is incorporated in a control circuit, such asschematically shown, that energizes a motor 19 and operates a pair ofclutches 20 and 21, which selectively connect a tape supply reel 22 or atake-up reel 23 to motor 19. Pulley 12 of switching normally closedcontact 35a and 36a to points of normally open contact 3512 and 36b. Theposition of the movable contacts 35 and 36 determines the connectionsmade between a bridge rectifier, comprising diodes 37, 38, 39 and 40,and coils 25a and 26a of clutch operating solenoids 25 and 26. Adropping resistor 41 is employed in the connection between the bridgerectifier and solenoid coils.

Sliding contact 18 of switching mechanism 10 is mounted to an indicator42 that may be positioned along a scale 43 having a plurality ofmarkings 44. Each marking of the scale indicates a position that relatesto a selected picture on a tape T extending between and wound aroundtape reels 22 and 23. Indicator 42 is accurately positioned relative toscale 43 by means of a fine hairline 45.

A typical example of operation follows:

Slide indicator 42 is positioned on scale 43 so that the hairline 45 isopposite the marking representative of a selected picture to be viewed.Movement of the indicator also causes contact 18 to slide along theelectrically conductive element 18a, and if this position also placescontact 18 into engagement with one of the electrically conductivesections 13a or 13b, it will condition the control circuit forenergizing motor 19, and engage the appropriate clutch as will movenonconductive section in the direction of contact 18. As an example, ifindicator 42 is positioned to the right of that shown in FIG. 1,bringing contact 18 into engagement with the electrically conductivesection 13b, and assuming onoff switch 30 is closed or on," momentaryclosure of switch 31 will energize a circuit to solenoid coil 26athrough switches 30-31, sliding contact 18, fixed contact l7, normallyclosed contacts 35a and 36a, and the bridge rectifier. In addition, aholding circuit is energized to relay coil 32, closing contacts 33.Motor 19 will then drive tape reel 23 through clutch 21, simultaneouslyrotating pulley 12 in a direction that moves the nonconductive section13c toward sliding contact 18. When section 13c alone engages contact18, the circuit energizing relay coil 32 is interrupted and contacts 33open, deenergizing motor 19 as well as solenoid coil 26a.

Should sliding contact 18 be moved to the left and into a position thatcontact is made with electrically conductive section 13a, relay coil 34is energized, reversing the movable contacts 35 and 36 and energizingsolenoid coil 25a. It will be apparent that motor 19 is also energized,together with the holding circuit including coil 32. The energizingcircuit for solenoid coil 252: extends from the AC power source throughsliding contacts 18, electrically conductive section 13a, fixed contact16, normally open but now closed contacts 35b and 36b, and the bridgerectifier.

FIG. 2 of the drawings illustrates a preferred analog computer mechanism24 for driving switch belt 13 at a rate which bears linear relationshipto the rate at which tape is wound upon and unwound from tape reels 22and 23. The need for such a mechanism is apparent since each additionalwinding of tape increases the effective diameter of take-up so that thespeed of tape travel increases or decreases depending on whetherwindings are being added or subtracted from the reels. In the past,thisproblem has been dealt with either by scaling the indicator toreflect the nonlinear relationship between reel displacement and tapemovement or by frictionally contacting the film or'tape and mechanicallylinkingthe indicator to the contact A build up of cumulative errorsattributable to slippage is customary although undesirable. v

Mechanism 24 essentially comprises a pair of spiral pulleys 46 and 47,each having a continuous groove beginning at a large outer diameter'andterminating at a smaller inner diameter. Both pulleys are mounted on acommon shaft 48 that is mechanically linked as by gearing to tape reel23. A cord 49, such as a radio dial cord, is fastened to the outergroove of one pulley, such as at point 46a, and to the inside groove ofthe other pulley, as at point 47a. Cord 49 is wound such that thediameter at the point of tangential contact of both pulleys is the same.Thus, as the cord is wound onto one pulley, it is wound off the other atthe same linear rate per degree of revolution, and that portion of cord49 which is unwound-from the pulleys(outside the pulley system) remainsa constant length. The cord outside the pulley system is entrainedaround a third pulley 50 that is mechanically linked with pulley 12 ofthe switching mechanism. For ease of assembly, cord 49 is made in twosections, each section being initially wound on respective pulleys, andthe free ends joined by'a tensioning spring, not shown.

In operation, pulleys 46and 47 are rotated in direct angularrelationship to the rotation of take-up reel 23, but in nonlinearrelationship to the rate of tape movement. On the other'hand, the spiralwindings of cord 49 are wound and unwound in linear relationship to themovement of tape T. The transformation of angular displacement ofpulleys 46 and 47 into movement of cord 49 as a linear function of filmortape travel is accomplished by selecting the radial pitch of thepulleys, the gear ratio from take-upreel to'pulleys, and insideandoutside pulley diameter in accordance with the followingrelationships:

I r t n I rr I 2) where iiigtit oifiih'i'bfiapeihdvefiit length of cord(or switch) movement K take-up reel O.D. take-up reel ID.

K thickness of film or tape radial pitch of pulley turns of take-up reelturns of pulley A preferred embodiment of this invention operatesswitching mechanism 10 off of the tape reel which serves as the take-upreel in the viewing system rather than the supply reel. However,inasmuch as the take-up reel and supply reels are mechanically linked bythe tape, it is also feasible to operate the switching mechanism fromeither one of the two reels. Nevertheless, it will be apparent that animportant advantage is gained by operating the switching mechanism fromthe take-up reel. In so doing, the relationships required forlinearizing the movement of the switching mechanism and making itdirectly proportional to tape movement remain the same even though thenumber of turns and amount of tape contained on various supply reels aredifferent.

Although a preferred embodiment of this invention has been illustratedand described, various modifications and changes may be resorted towithout departing from the spirit of the invention or the scope of theattached claims, and each of such modifications and changes iscontemplated.

What is claimed is:

1. In a control circuit for operating a motor, a switching mechanismcomprising: a pair of spaced, movable contacts, a slidable contact thatmay be preset in various positions along a predetermined path, meansresponsive to operation of said motor and controlled by said switchingmeans for moving said pair of movable contacts along said predeterminedpath, and circuit means for energizing said motor when either one ofsaid movable contacts engages said slidable contact and de-energizingsaid motor when neither movable contact engages said slidable contact,an engagement with one movable contact and said slidable contact causingsaid movable contacts to move in one direction along said predeterminedpath while an engagement with the other movable contact and slidablecontact causes said movable contacts to move in the opposite direction.I

I 2. In the control circuit of claim 1, said switching mechanismcomprising a continuous belt having electrically conductive sectionsseparated by a nonconductive section, a pair of wiping contactsengageable with said pair of electrically conductive sections, saidmotor control circuit being conditioned for energizing said motor wheneither of said electrically conductivesections engages said slidablecontact.

3. The apparatus of claim-1 and further comprising a scale that extendsalong said predetermined path and an indicator mounted for movementalong said Scale, said sliding contact being connected to saidindicator.

4. A film or tape positioning apparatus comprising: a pair of reelshaving a film or tape connected therebetween and adapted to be wound andunwound from said reels; a motor; means for selectively clutching saidmotor to one or the other of said reels; and a control circuit includinga switching mechanism for energizing said motor and clutching said motorwith one of said reels, said switching mechanismcomprising a pair ofmovable contactsand a sliding contact that may be positioned in one ofseveral positions along a predetermined path, means responsive tooperation of said motor for simultaneously moving said movable contactsinthe same direction as said predetermined path to bring said movablecontacts into engagement with said slidable contact at variouspositions, said control circuit energizing said motor and clutching saidmotor with one of said reels when one of said movable contacts engagessaid slidable contact, an engagement between one of said movablecontacts and said slidable contact clutching said motor with one reelwhile a contact between the other movable contact and said slidablecontact clutches said motor with the other reel.

5. The apparatus of claim 3, said means for moving said movable contactsincluding an analog computer for moving said contacts at a rate linearlyproportional to the rate of tape movement.

6. The apparatus of claim 4, said means for moving said movable contactscomprising a pair of substantially identical spiral pulleys mechanicallyconnected to one of said reels, a cord wound around said spiral pulleys, one end of said cord being secured at the large diameter groove ofone pulley and the other end being secured at the small diameter grooveof the other pulley, said cord being wound around said pulleys such thatthe diameter at the point of tangential contact of both pulleys issubstantially the same, said cord including a section between thepulleys that remains a constant length as the cord is wound onto onepulley and off the other pulley, and means engaged by said cord sectionfor moving said movable contacts.

7. The apparatus of claim 6, one of said pair of reels being a supplyreel and the other a take-up reel, said spiral pulleys being connectedto the take-up reel, said spiral pulleys being constructed in accordancewith the relationships K,= K,K,, and K,= K,K,, where V take-up reel (1D.talreaip reel I.D

pulley 0.1). pulley ID. and

thiokness of film or tape, radial pitch of pulley and turns of take-upreel, turns of pulley and K length of film or tape movement length ofcord movement

1. In a control circuit for operating a motor, a switching mechanismcomprising: a pair of spaced, movable contacts, a slidable contact thatmay be presEt in various positions along a predetermined path, meansresponsive to operation of said motor and controlled by said switchingmeans for moving said pair of movable contacts along said predeterminedpath, and circuit means for energizing said motor when either one ofsaid movable contacts engages said slidable contact and de-energizingsaid motor when neither movable contact engages said slidable contact,an engagement with one movable contact and said slidable contact causingsaid movable contacts to move in one direction along said predeterminedpath while an engagement with the other movable contact and slidablecontact causes said movable contacts to move in the opposite direction.2. In the control circuit of claim 1, said switching mechanismcomprising a continuous belt having electrically conductive sectionsseparated by a nonconductive section, a pair of wiping contactsengageable with said pair of electrically conductive sections, saidmotor control circuit being conditioned for energizing said motor wheneither of said electrically conductive sections engages said slidablecontact.
 3. The apparatus of claim 1 and further comprising a scale thatextends along said predetermined path and an indicator mounted formovement along said scale, said sliding contact being connected to saidindicator.
 4. A film or tape positioning apparatus comprising: a pair ofreels having a film or tape connected therebetween and adapted to bewound and unwound from said reels; a motor; means for selectivelyclutching said motor to one or the other of said reels; and a controlcircuit including a switching mechanism for energizing said motor andclutching said motor with one of said reels, said switching mechanismcomprising a pair of movable contacts and a sliding contact that may bepositioned in one of several positions along a predetermined path, meansresponsive to operation of said motor for simultaneously moving saidmovable contacts in the same direction as said predetermined path tobring said movable contacts into engagement with said slidable contactat various positions, said control circuit energizing said motor andclutching said motor with one of said reels when one of said movablecontacts engages said slidable contact, an engagement between one ofsaid movable contacts and said slidable contact clutching said motorwith one reel while a contact between the other movable contact and saidslidable contact clutches said motor with the other reel.
 5. Theapparatus of claim 3, said means for moving said movable contactsincluding an analog computer for moving said contacts at a rate linearlyproportional to the rate of tape movement.
 6. The apparatus of claim 4,said means for moving said movable contacts comprising a pair ofsubstantially identical spiral pulleys mechanically connected to one ofsaid reels, a cord wound around said spiral pulleys, one end of saidcord being secured at the large diameter groove of one pulley and theother end being secured at the small diameter groove of the otherpulley, said cord being wound around said pulleys such that the diameterat the point of tangential contact of both pulleys is substantially thesame, said cord including a section between the pulleys that remains aconstant length as the cord is wound onto one pulley and off the otherpulley, and means engaged by said cord section for moving said movablecontacts.
 7. The apparatus of claim 6, one of said pair of reels being asupply reel and the other a take-up reel, said spiral pulleys beingconnected to the take-up reel, said spiral pulleys being constructed inaccordance with the relationships Kr KtKn and Kl KtKn2, where